linesearch: Line searcher function
In xinchoubiology/RcppGLM: Parallel Generalization Linear Mode

linesearcher method for GLM class

define lineseaher method

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wolfe_linesearcher(a = 0.01, b = 0.9, t0 = 1, tol = 0.001, ...)

backtrack_linesearcher(a = 0.4, b = 0.8, ...)

`a`	m1 in f(x<e1><b5><a2> + td) <= f(x<e1><b5><a2>) + m<e2><82><81>t<<e2><88><87>f(x<e1><b5><a2>) , d>
`b`	m2 in <<e2><88><87>f(x<e1><b5><a2> + t*d), d> >= m<e2><82><82><<e2><88><87>f(x<e1><b5><a2>), d>
`t0`	init step size
`tol`	tolerance
`a`	f(x + t * <ce><94>x) <e2><89><a6> f(x) + a.t<<e2><88><87>f(x), <ce><94>x
`b`